The rate of evaporation, especially for water, is a quantity useful in many applications. Not only is the rate of evaporation of water useful in meteorology, but also in the control of manufacturing and storage where moisture sensitive materials are handled. Furthermore, in agriculture especially where irrigation is practiced, the control of water resources is significantly important. The knowledge of the evaporation rate is an important factor in such agricultural practices. Moreover, knowledge of the evaporation rates in libraries and museums is important for the preservation of books and antiques.
An evaporimeter for measuring the evaporation rate of a liquid is described in U.S. patent application Ser. No. 139,738, filed Apr. 14, 1980, entitled "APPARATUS AND METHOD FOR MEASURING THE RATE OF EVAPORATION OF A LIQUID" by R. Williams, now U.S. Pat. No. 4,324,132, issued Apr. 13, 1982. The apparatus of the evaporimeter operates on the principle of hydraulic continuity using capillary action in a capillary system formed of a capillary tube carrying an evaporable liquid, such as water, to a large evaporation surface of fibrous material. Liquid evaporated from the surface of the liquid is replenished by the liquid in the tube. The rate of movement of the tube liquid is a measure of the evaporation rate.